In the development trend of increased use of function modules and decreasing size, stacking space of a mobile phone becomes increasingly tight. Currently, for PCB placement of the mobile phone, it is very crowded in a top space of the mobile phone, and a large speaker has to be placed on a bottom of the mobile phone.
In order to ensure the mobile phone picks up a user's voice and eliminates environmental noise normally, the mobile phone is designed to adopt a dual-microphone de-noising design. The dual-microphone de-noising algorithm requires that: signal-to-noise ratio of the primary microphone and that of the auxiliary microphone shall have obvious difference; if the difference is greater, it is more favorable to de-noising. Therefore, the primary microphone is arranged on the bottom of the mobile phone, as close to the mouth of the human as possible, to pick up the voice in the handheld mode; and the auxiliary microphone is arranged on the top of the mobile phone to pick up the environmental noise.
This placement design may be a test for the hands-free call quality of the mobile phone: the hands-free call may require a high volume of the speaker, but the speaker and the primary microphone may be too close; the voice on the other end, after being broadcast by the speaker, can be picked up by the native primary microphone and sent to the other end, which may cause a serious echo problem. The echo means that, during a call, the voice from the other end, after being broadcast by the speaker, is picked up by the native microphone and sent to the other end, and the sound of one's own voice at the other end can be heard on the mobile phone of oneself, this sound being the echo, and the echo can be serious during a hands-free call.
Therefore the existing technology still needs to be improved and enhanced.